The present invention relates to pipe handling systems for handling a variety of oil field tubular pipe, such as drill pipe, production tubing, well casing, and riser pipe. More particularly, the present invention relates to pick-up and lay-down systems for use in offshore drilling operations where pipe is picked up from a pipe rack, placed in a trough, and the trough and pipe moved to a position on the drill floor where the pipe may be removed from the trough.
There are several prior art methods of picking up and laying down drill pipes, casings, collars, and risers. The most common method, which is the only method on jack-up drill rigs and platform drill rigs, is also the most primitive and dangerous. A worker must first tie a sling around a bundle of pipe (the bundle will weigh up to 10 short tons) and then guide the pipe as it is lifted off of the pipe rack. To do this, a worker must stand on a stack of pipe which may be as high as ten feet, which in itself could be very dangerous.
When the pipe is raised above the pipe rack it is then swung over to a V-door ramp or dragway where another worker must grab the pipe bundle and guide it down in place on the ramp or dragway. Often, a worker is bumped around and injured when the crane swings the pipe out too far. After the pipe is set in the dragway, a cat line is tied to the end of the pipe and the pipe is pulled up the ramp to the drill rig floor by the combination of the cat line and an air tugger. This final operation often damages the pipe.
There are several different types of pick-up and lay-down machines being used on offshore operations, however, these prior art devices have been used with very limited success. One example of those offshore systems is the B C Manufacturing Co. Model 25 unit which is primarily designed for onshore operations, but has been used offshore on occasions.
The Model 25 requires a support cable to be attached at one end to the derrick of the drill rig. The other end of the cable is attached to a winch bolted to the pipe rack. A trough is provided for receiving the pipe, one pipe at a time. The pipe is rolled into the trough and the trough pulled along the support cable to the drill floor. Unfortunately, this system is unable to handle the heavier pipes, such as risers and longer casing pipe, because of the sag produced in the support cable.
Another type of pick-up and lay-down machine is the Mereco Model 44. The Model 44 operates to transfer drill pipes, casings, and risers to the drill floor. The Mereco Model 44 is stationary and requires a crane to load the pipe, casings and risers from the pipe rack to the trough. The trough and pipe is then lifted to the drill floor by a series of hydraulic rams. The Model 44 is capable of handling double and triple pipe groups at a time.
Western Gear also makes a prior art pick-up and lay-down machine for use on offshore operations. This unit is called the Pipe Racker. The Pipe Racker is stationary and requires a slot approximately 4 feet by 8 feet to be cut into the drill floor for installation. This type of modification is expensive, and most drilling contractors who consider using such a machine do not like to cut slots into their drill floors. The Pipe Racker is extremely expensive and complicated, involving many moving parts. Additionally, it can handle only certain kinds of pipe, for example, the lighter pipes, such as drill pipe and casing pipe, or the heavier pipes, such as the collars and riser pipes. A crane is required to load the pipe into a trough which is pushed up to the drill floor by a hydraulic system of rams.